Cancare-a herbal formulation inhibits chemically induced tumours in experimental animals

Cancer chemopreventive potential of Cancare, a multi-herbal formulation on chemically induced tumours was studied by N-nitrosodiethylamine (NDEA) induced hepatocarcinogenesis in rats and 20-methylcholanthrene (20-MC) induced sarcoma development in mice. Oral administration of Cancare was found to inhibit the liver tumour development induced by N-nitrosodiethylamine. Animals administered with NDEA had visible liver tumours by the end of 30th weeks and the liver weight was raised to 6.1 +/- 1.4 g/ 100 g body wt. None of the animals treated with Cancare (150 mg/ kg) developed any visible liver tumours by this period and the liver weight was 3.0 +/- 0.6 g/ 100 g body wt. Gamma-Glutamyl transpeptidase, a marker of hepatocellularcarcinoma, which was raised to 83.7 +/- 8. 9 U/l in serum of NDEA treated group was reduced to 35.2 +/- 6.1 U/l by simultaneous administration of Cancare. Elevated levels of serum alkaline phosphatase, glutamate pyruvate transaminase, bilirubin, liver glutathione S-transferase, glutathione and gamma-Glutamyl transpeptidase in the NDEA administered group was significantly reduced by Cancare administration. Cancare administration inhibited the sarcoma development and increased the life span of mice administered with 20-MC dose dependently. All animals in the control group developed sarcomas by 150th day and dead by 174th day after 20-MC administration. Cancare administration (30 mg and 150 mg/kg) inhibited the sarcoma development (46.7 and 60%) as well as increased the life span (53.3 and 66.7%) as estimated on 240th day after 20-MC administration. The results are indicative of the chemopreventive potential of Cancare against chemically induced neoplasmas.     

Tissue specificity of the decrease of cattle lymphocyte DNA methylation during chronic lymphoid leukemia]

It has been found that the content of m5C in the DNA preparations tested have been revealed. The DNAs from normal and leukemic lymphocytes of blood, lymphonodi and spleen differ in ther acceptor ability in the reaction of heterologous methylation in vitro, induced by DNA-methylase from Enterobacter cloacea in the presence of [3H-methyl]S-adenosyl methionine: the ratio of radioactivities in methylated cytosine and adenine residues (m5C/m6A) in leukemic lymphocyte DNA is much lower than in healthy animals' lymphocytes. The decrease in the methylation of DNAs from various lymphoid organs of animals with chronic lymphoid leukemia is well correlated with the impairment. No significant changes of the m5C level and the acceptor ability of the in vitro reaction of heterologous methylation of cow lymph lymphocyte DNA have been observed. The data obtained may be interpreted in terms of tissue (cell) specificity or differences in the degree of DNA methylation under conditions of chronic lymphoid leukemia. It is assumed that the changes in DNA methylation may underlie the disturbances in the regulation of activity of the leukemic cell genetic mechanisms.     

Lipid composition of immunocompetent organs of tumor-bearing rats

A comparative study of phospholipid composition of thymus, spleen, bone marrow, liver and peritoneal exudate with sarcoma 45-bearing and normal rats was carried out. It was found that substantial changes in total phospholipid and cholesterol contents are observed only in peritoneal exudate of tumour-bearing animals. Some alterations were revealed in the content of individual fractions of investigated organs. The most pronounced changes in the contents of individual phospholipid fractions were found in peritoneal exudates of rats with sarcoma 45.     

3-Methylcholanthrene induces phenobarbital-induced cytochrome P-450 hemoprotein in fetal liver and not cytochrome P-448 hemoprotein induced in maternal liver of rats

The characteristic nature of the drug-metabolizing system in fetal liver microsomes of rats was investigated. The aminopyrine(AM)- and the hexobarbital (HB)-metabolizing activities in fetal liver microsomes of the 21st day of pregnancy were induced by the maternal administration of 3-methylcholanthrene (3-MC) once daily on the 18th and the 19th day of pregnancy, while they were inhibited in maternal liver microsomes. The inductions of the AM- and the HB-metabolizing enzymes in fetal liver microsomes of rat by the maternal administration of 3-MC occurred exclusively in fetal period and simultaneously hemoprotein like phenobarbital-induced type P-450 different from that in maternal liver microsomes was newly induced in fetal liver microsomes of rats.     

Tissue-specific hypomethylation and expression of rat phosphoenolpyruvate carboxykinase gene induced by in vivo treatment of fetuses and neonates with 5-azacytidine

Rat fetuses of 17-19-day gestation were injected in utero with 5-azacytidine (two to three daily injections of 40 micrograms/fetus). Neonates were injected with seven daily injections (1 mg/kg). DNA samples were isolated from the fetal and neonatal livers and neonatal spleen and subjected to analysis of their methylation status. Overall methylation was analyzed by the nearest-neighbor analysis (at CpG sites) and the pattern of methylation at CCGG sites by Southern blot analysis using phosphoenolpyruvate carboxykinase (PEPCK) sequences as probes. While DNAs from the liver and spleen undergo hypomethylation to the same extent in response to the 5-azacytidine treatment, the changes in the methylation patterns of the PEPCK gene in the two tissues are strikingly different. The changes observed indicate that a decrease in the methylase activity (inhibition by 5-azacytidine) results in site- and tissue-specific hypomethylation. The tissue-specific changes in the methylation pattern are associated with a tissue-specific expression of the PEPCK gene. Although the gene is hypomethylated by azacytidine in both liver and spleen, it is expressed only in the liver. The expression of already active genes (PEPCK in the kidney and albumin in the liver) is not further enhanced by the drug.     

Secondary structure and methylation of DNA in reinoculated tumors and cultures of embryonic cells transformed by oncogenic viruses]

Using the kinetic formaldehyde method the concentration of secondary structure defects (SSD) in the DNAs of ascite leukosis L 1210 cells and cultures of hamster embryonic cells transformed by virus SV-40 and polyoma was evaluated. It was found that this concentration was considerably higher than in the DNAs from normal liver and primary culture of mouse embryonic cells. The occurrence of the defects in malignant cell DNAs is not due to enzymatic degradation of DNA. Using thin-layer chromatography the content of m5C in the DNAs from 17 sources (transformed cell cultures, experimental tumours and liver cells of mouses with Ehrlich ascite carcinoma) were determined. The methylation level for all these DNAs was higher than for normal mouse and rat liver DNAs. No correlation between the SSD concentration and m5C content in the DNAs studied was observed.     

Differential methylation of mitochondrial and nuclear DNA in cultured mouse, hamster and virus-transformed hamster cells. In vivo and in vitro methylation

Information has been lacking as to whether mitochondrial DNA of animal cells is methylated. The methylation patterns of mitochondrial and nuclear DNAs of several mammalian cell lines have therefore been compared by four methods: (1) in vivo transfer of the methyl group from [methyl-³H]methionine; (2) in vivo incorporation of [³²P]orthophosphate and a combination of (1) and (2); (3) in vivo incorporation of [³H]deoxycytidine; (4) in vitro methylation of DNAs with ³H-labeled S-adenosylmethionine as methyl donor and DNA methylase preparations from L cell nuclei. The cell lines were mouse L cells, $\text{BHK21}\text{C13}$, $\text{C13}\text{B4}$ (baby hamster kidney cells transformed by the Bryan strain of Rouse sarcoma virus), and PyY (BHK cells transformed by polyoma virus). DNA bases were separated chromatographically, using 5-methylcytosine, 6-methylaminopurine and, in some cases, 7-methylguanine as markers.Mitochondrial DNA was found to be significantly less methylated than nuclear DNA with respect to 5-methylcytosine in all cell types studied and by all methods used. The relative advantages and disadvantages of each method have been discussed. The level of 5-methylcytosine in mitochondrial DNA as compared with that in nuclear DNA was estimated as one-fourth to one-fourteenth in various cell lines. The estimated 5-methylcytosine content per circular mitochondrial DNA molecule (mol. wt 10 × 10⁶) was about 12 methylcytosine residues for L cells and 24, 30 and 36 methylcytosine residues for BHK, B4 and PyY cells, respectively. Relative to cytosine residues, the estimate was one 5-methylcytosine per 500 cytosine residues of mitochondrial DNA and one 5-methylcytosine per 36 cytosine residues of nuclear DNA from L-cells. The values for methylcytosine of mitochondrial DNA are presumed to be maximal. PyY cells as compared with other cells had the highest methylcytosine content of both mitochondrial and nuclear DNA as estimated by method (3). No methylation of nuclear DNA was observed in confluent L cells.Evidence for the presence of DNA methylase activity associated with mitochondrial fractions was obtained. This activity could be distinguished from other cellular DNA methylase activity by differential response to mercaptoethanol. Radioactivity from ³H-labeled S-adenosylmethionine was found only in 5-methyl-cytosine of DNA.     

Dose-dependence, sex- and tissue-specificity, and persistence of radiation-induced genomic DNA methylation changes

Radiation is a well-known genotoxic agent and human carcinogen that gives rise to a variety of long-term effects. Its detrimental influence on cellular function is actively studied nowadays. One of the most analyzed, yet least understood long-term effects of ionizing radiation is transgenerational genomic instability. The inheritance of genomic instability suggests the possible involvement of epigenetic mechanisms, such as changes of the methylation of cytosine residues located within CpG dinucleotides. In the current study we evaluated the dose-dependence of the radiation-induced global genome DNA methylation changes. We also analyzed the effects of acute and chronic high dose (5Gy) exposure on DNA methylation in liver, spleen, and lung tissues of male and female mice and evaluated the possible persistence of the radiation-induced DNA methylation changes. Here we report that radiation-induced DNA methylation changes were sex- and tissue-specific, dose-dependent, and persistent. In parallel we have studied the levels of DNA damage in the exposed tissues. Based on the correlation between the levels of DNA methylation and DNA damage we propose that radiation-induced global genome DNA hypomethylation is DNA repair-related.     

DNA methylase: purification from ascites cells and the effect of various DNA substrates on its activity.

DNA methylase has been purified 405-fold from Krebs II ascites cells. The purified enzyme is homogeneous on SDS-poly acrylamide gel electrophoresis (molecular weight about 80,000) and the only product of the reaction with DNA is 5-methyl cytosine. Both native and denatured DNA are methylated by the enzyme; with calf thymus DNA the double stranded form is the better substrate but the enzyme preferentially methylates single stranded E.coli DNA even in "native" preparations. Our results do not support a mechanism whereby the enzyme methylates DNA by binding irreversibly and "walking" along it. By measuring maximum levels of methylation of DNAs from different sources we have estimated the proportion of unmethylated sites present in them. Homologous ascites DNA can be methylated, but only to about 5% of the level of the best substrate, undermethylated mouse L929 cell DNA. DNA isolated from growing cells or tissues is a better substrate than DNA from normal liver or pancreas, or from stationary cells.     

Liver-specific expression of a Qa-encoded class I gene is associated with DNA hypomethylation.

DNA methylation of two murine major histocompatibility complex (H-2) class I genes was examined in hybridizations to MspI and HpaII chromosomal DNA restriction digests. Q10, which exhibits liver-specific expression, and H-2Kb, a transplantation antigen gene, were examined in liver, spleen, thymus, and cell-line DNAs. Unmethylated Q10 gene sequences were detected only in the liver, whereas the H-2Kb gene was unmethylated in all tissues examined.     

Correlation of the increase in DNA methylation and antioxidant activity of mouse liver nuclear lipids after administration of antioxidant and in Ehrlich ascites carcinoma

The content of 5'-methylcytosine in total DNA of mouse liver increases 2--2,5-fold 3 hrs after a single intraperitoneal injection of antioxidant (4-methyl-2,6-ditretbutylphenol) (20 or 60 mg per 1 kg of body weight) and makes up to 2--2.4 mol.%. The methylation of liver DNA is also increased more than 2-fold in Ehrlich ascite carcinoma. The DNA isolated from mouse liver after administration of antioxidant or during cancer growth markedly differs from liver DNA of intact animals in its CH3-accepting ability under in vitro methylation by the methylase complex from Enterobacter cloacea. The changes in DNA methylation in mouse liver under the effects of antioxidant and in Ehrlich ascite carcinoma are correlated with the changes in the antioxidant activity of liver nuclear lipids.     

The 5''-cytosine in CCGG1 is methylated in two eukaryotic DNAs and Msp I is sensitive to methylation at this site.

Novikoff rat hepatoma and bovine liver DNAs were digested with Msp I or Hpa II. Restriction fragments were end-labeled using [alpha-32P]-dCTP and the Klenow fragment of E. coli DNA polymerase I and then digested to 2'-deoxyribonucleoside-3'-monophosphates using micrococcal nuclease and spleen phosphodiesterase. Mononucleotides were separated by two-dimensional thin layer chromatography, localized by radioautography, and the [32P]-label quantitated by scintillation spectrometry. This method, based on known specificities of Msp I and Hpa II, shows that CCGG, CMGG, and MCGG (M refers to 5-methylcytosine) occur at frequencies of 89.6%, 1.4%, and 9.0%, respectively, in the rat DNA and at 41.6%, 48.3%, and 10.0%, respectively, in the bovine DNA. [32P] recovery in 3'-5-MedCMP from end-labeled Msp I digests was negligible compared to recovery from Hpa II digests. Hence, Msp I is sensitive to methylation at the 5' cytosine in the sequence CCGG.     

Morphological and biochemical study of the organs of immunogenesis during the growth of established glioblastoma multiforme in albino rat brain]

Morphological changes in the lympho-reticular organs (the thymus, lymph nodes, spleen) were studied and the content of the RNA was determined by the biochemical method in 92 rats during the growth of the glioblastoma multiforme (strain 101/12) in the brain. The reaction of the organs of immunogenesis depended on the stage of the disease. On the 6th day after the transplantation of the tumour the increased activity of the epithelial-reticular portion of the thymus, hyperplasia of the follicles in the lymph nodes, and increased produciton of the RNA was observed. As to the tumour-bearing animals the destruction of the lymphoid elements and decreased synthesis of the RNA was noted. A giradual cell depletion of the spleen was revealed morphologically.     

Comparative study of the repeated nucleotide sequences in DNA from differentiated tissues and tumors]

DNA renaturation kinetics was measured for the genomes of normal (spleen) and malignant (plasmacytoma) mouse tissues and for DNA from liver, sperm and developing embryos of the loach. It has been shown that the measuring of DNA renaturation kinetics makes it possible to reveal differences in the content of certain fractions of the repetitions in the genomes of different species. Moreover, differences in the distribution of the repetitions between hetero- and euchromatine can be identified. Loach embryo DNA (blastula stage) was shown to contain larger amount of the fraction renaturing at Cot less than 10(-2) as compared to liver and sperm DNAs (by 5%). An enrichment with respect to the intermediate repetitions (10(-2) less than Cot less than 10(2)) was found in the mouse plasmacytoma DNA as compared to the spleen DNA. The nature of these distinctions is discussed.     

Anti-ageing effects of protocatechuic acid from Alpinia on spleen and liver antioxidative system of senescent mice

The effects of Alpinia protocatechuic acid (PCA) on spleen and liver antioxidant system in aged rats have been studied. Alpinia PCA, a phenolic compound, was first isolated from the dried fruits of Alpinia Oxyphylla Miq. in our laboratory. Young and aged rats were injected intraperitoneally with Alpinia PCA at single doses of 5 mg kg(-1) (low dose) or 10 mg kg(-1) (high dose) per day for 7 days. The activities of endogenous antioxidants and the content of lipid peroxide in spleen and liver were assayed. Compared with young group, aged rats had significantly lower splenic weights, lower activities of glutathione peroxidase (GSH-PX) and catalase (CAT), higher level of malondialdehyde (MDA) in spleen and liver. The results proved that Alpinia PCA significantly elevated the splenic weights, increased the activities of GSH-PX and CAT and decreased the MDA level of aged rats. All these suggested that Alpinia PCA was a potential anti-ageing agent, and its effects on spleen and liver were achieved at least partly by promoting endogenous antioxidant enzymatic activities and normalizing age-associated alterations. It may be therapeutically useful to minimize age-associated disorders where oxidative damage is the major cause.     

Tissue-specific differences in DNA methylation in various mammals

The only naturally occurring modified base in vertebrate DNA is 5-methylcytosine. Using a precise high-performance liquid chromatographic analysis of DNA enzymatically digested to deoxynucleosides, we have shown that rats, mice and four types of monkey display tissue-specific as well as species-specific differences in the extent of methylation of their cytosine residues. Several similarities in the patterns of tissue-specific DNA methylation in these mammals and in the previously studied human samples were observed. Compared to most other types of DNA examined, brain and thymus DNAs were hypermethylated, which suggests that this hypermethylation is a determinant or a necessary byproduct of mammalian differentiation. In all of the studied rodents and primates, the highly repeated DNA sequence fraction was more methylated than the moderately repetitive or single copy fractions. The tissue-specific differences in overall DNA methylation showed no correlation with what is known about average cell turnover rates nor with the percentage of the genome that is transcribed. Liver regeneration in the rat following partial hepatectomy did not detectably alter 5-methylcytosine levels in liver DNA. A considerable increase in the extent of methylation of total liver DNA was observed during normal development of the rat. The latter phenomenon may be due to a major change in the cellular composition of the liver.